Add option to set welcome page view for libraries with a document set

[T-LeGranc]

There is currently still no way to set welcome page view for libraries with a document set.

It looks like there has been some attempt to add this in schema 2018-07, but this entry does not actually do anything. Moreover, as mentioned in comments in the original issue, it does not seem to make sense for this to be on the DocumentSetTemplate because this setting is specific to the document library and its views. It should be a setting at the library level.

This has been a long-standing issue with SharePoint Online provisioning that still has no viable workaround other than simulating clicks in a browser... Please see discussion and links in this SharePoint Stack Exchange question for further details.

[aukebgit]

we need this!

[zenlord]

I added my solution to the other issue (which however has been closed, so linking it here):
#190 (comment)

//EDIT: this is not working. The property 'SchemaXml' is read-only.
Cross-link: https://sharepoint.stackexchange.com/a/314039/68024