Hey @linuxgurugamer,
so sorry for the confusion on my part. Regarding the supposed EEX problem, I was actually wrong three times: Firstly, that I was referring to Filter Extensions and not EEX, secondly, that I assumed that the "hide unpuchased parts" functions within Filter Extensions would also work with the original light blue filters and not just the light green ones added by Filter Extensions, and thirdly, that there was any compatibility problem between Filter Extensions and JC in the first place (now that I know what to look for, I did some test installations and everything seem to work as it should).
Regardless of the confusion over this aspect, I still think that JC would benefit from being able to set the "hide unpurchased" feature to always on. Whilst JC is great in that, unlike Filter Extensions, it can actually modify the contents of the standard part filters, I usually use the "hide unpurchased" feature, especially when I am running a part-heavy installation. My problem is that the function is automatically turned off as soon as I leave the VAB/SPH. If it were possible to set the "Hide unpurchased" function to always be on, there would be a much better distinction between the R&D building, where you would not only go to research parts, but also to purchase them (if you disable the "No entry purchase required on research" option at the beginning of a campaign), and the VAB and SPH, where you can only see the parts that are actually available for your space program, without all the parts you don't need (for now).
I hope that clarifies things. Nevertheless, I am very grateful to you for taking the time to listen to these ideas for incremental improvement