I expected to see: All custom fields of the group "Soort organisatie"
Instead, I got: Not all fields, and less than my previous ticket...
Could this have something to do with the conditionality of the fields? To me it seems that S&F can't access these when no Post Type, where these fields belong to, are available
As SearchFilter Pro is not a Toolset product, I expect that it doesn't know anything about Toolset Custom Field Groups or the definitions for Toolset custom fields.
I imagine that when it offers fields to be used as search filters it determines what fields to offer based upon scanning existing posts to see what custom fields they have.
So if you create a Toolset field group with fields 'One' and 'Two', and you then publish a post of some type where these fields are available and you provide a value for 'One' but not for 'Two', then when SearchFilter Pro scans to find what custom fields exist for this post type, in the database it will come across 'One' (actually, 'wpcf-one', which is the post meta key used for such a field), but it won't know anything about 'Two', because no posts have a value for the field saved in the database.
If you make sure there are posts with values for all of the fields you want to include, I expect the plugin should be able to find them.