If anyone is still looking for an option to make dimension unselectable (for example in the table):
1. Create an alternate state in master items: i.e. NewState1
2. Edit the table that you want to have dimensions unselectable and go to alternate states --> change to your NewState1
3. Use set analysis in the measures in this table to ensure these are referring to the default state, not NewState1 by adding {$} to the expression like that: Sum({$}Measure).
As a result it is still technically possible to click and select the dimensions in this table, but it won't have any effect as no other objects are using this alternate state, and measures in this object are referring to default state {$}.
If you want to just make one of the columns/dimensions unselectable that solution won't work.
