Currently the site collection URLs are fixed as https://tenant.sharepoint.com and cannot be changed. This does not fit with flexible cloud-based solutions - business needs will inevitably result in an organisation changing it's name during its lifetime (mergers, acquisitions, rebranding etc). While it may not be possible to change it so that entirely custom domains are used (eg contoso.com, instead of sharepoint.com), it must be possible to allow the sub-domain to be changed (eg. newtenant.sharepoint.com)? Please?

Migrating an entire organisation (likely to include Exchange, Skype, Sharepoint and Onedrive data!!) to a new Tenancy is absolutely not a viable option.

Please allow javascript customization and css branding/theming in the new document library experience. A custom cross-site navigation is one example that is used by many customers. Also many customers want their intranet branded in a different color but office ui fabric blue.
JSLink is also used very often. And don't Forget about all the third-party forms solution provider like Nintex and others.
The new experience provides many advantages, but without customizations it is just not usable for larger intranets anymore.

This limit has always been a bit laughable, and is even more so as we develop more client side applications. In SharePoint 2007 we didn't have this limit and were allowed to make our own mistakes. Now that hardware is so much more powerful, we need this limit removed so that we can build enterprise-class applications.

So Infopath 2013 is supported in 2016, but SharePoint really needs a full modern full-featured forms editor. FoSL looks promising but the functionality is not clear at this time.

Current term set based solution is not usable at all in real life multi site collection scenarios.

Office 365 / SharePoint online needs to support opening PDF documents in SharePoint directly to client application (Adobe Acrobat Pro/DC).

As of this request, technical support has stated the only way to open PDF files in Acrobat is to download/save them.

SharePoint On Premise has supported this feature for some time.

Adobe PDF files are as common and Microsoft Office Suite documents and must be editable directly to/from SharePoint Online without the need to down/save edit, and upload which adds user overhead and lowers productivity.

Please change how SharePoint generates links to uploaded documents and site pages, so that URLs with spaces will replace %20 with a dash instead. Most CMS tools including blogs do when generating SEO friendly URLs. Links with %20 throughout are too difficult to read.

This feedback site is a perfect example:

This:
https://sharepoint.uservoice.com/forums/282887-customer-feedback-for-sharepoint-server

is easier to read than this:
https://sharepoint.uservoice.com/forums/282887%20customer%20feedback%20for%20sharepoint%20server

This is essential and needs to be easy to find instead of hacking the URL every time you need to sign in as a different user.

Could we please have the ability to create Wikis in SharePoint that look like TechNet or Wikipedia? Please try to make things more simple. Do not over complicate it again.

Something I find myself wanting to do pretty frequently is storing an email attachment somewhere into SharePoint or OneDrive for Business. I want to simply drag the attachment from Outlook directly into SharePoint or OneDrive in the browser. Alas, I cannot. I am forced to save the attachment somewhere (my Desktop, most likely) then either drag+dropping it into SharePoint/OneDrive or using the upload function in SharePoint/OneDrive to get it uploaded.

It should be easier than that. Microsoft, please consider adding this functionality to get even more user-friendly integration between your suite of products.

Allow custom fields in SharePoint calendar available to view and update from Outlook

Document Sets in modern document libraries

We have multiple applications where our users want to integrate a SharePoint calendar with their Outlook calendars and the inability to do this with meeting requests prevents the applications from being really functionally useful.

Please stop opening links in a new tab by default in modern pages.

It is against standard web behaviour (https://www.w3.org/TR/2012/NOTE-WCAG20-TECHS-20120103/G200), and is confusing to users when they end up with 10+ tabs open when navigating even the simplest site.

Make it optional by all means, it makes sense in a number of cases, just please not by default.

Please provide the capability to change the header of the new modern pages (i.e. the large banner graphic on which the title is sitting. It currently means page content starts half-way down the screen which isn't the best use of space.

Allow for permission to be set on views. We would like to be able to use lists for submitting user data but do not want them to see all of the columns available in the list.

Content types are an essential part of SharePoint. One issue that has been around since SharePoint 2007 is the absence of an overview of all applied content types. Why is this important? Try to delete a content type and you get the message it's still in use. Good luck finding out where. This is very frustrating and time consuming. That's why I vote for an overview where you can see where the content types are applied.