Greetings!
i recently installed your mod and think its awesome sadly it dosnt works well in my play.
somehow the dropdown menu to chose what belt level to use is Empty!
it only shows the default yellow belt and the dropdown menu has no entrys at all.
so i cant utilize your tool to the fullest.
I play With Bobs Logistics. this adds a tier before Yellow (white) and some faster ones.
Any idea why the Belt Picker stays empty? the other pickers work like expected i can chose all the Drills and poles Bob Offers.

Update : Once i disable "Bob's Logistics mod" https://mods.factorio.com/mod/boblogistics the belt picker works again. seems to be a incompatibility.
Update 2: i tried to add Bob as a optional Dependency in your Mod to make yours load after but this didnt fixed the issue. further testing showed bob changes the subgroup for belts to "bob-logistic-tier-X" where X ranges from 0 to 5
Update 3 : I Added the respective Subgroups to the filter in line 1226 of your Control lua. this sadly also adds all the inserters that Bob Adds. also the two highest tiers dont have corrsponding Loaders. which makes your mod fail to place a blueprint if one of the tier 4 or 5 belts is selected ... this gets more and more complicated -.- i give up for now but hopefully gave you enough pointers to make your mod Bob Compatible.

Thanks for looking into it!
My first idea is - instead of messing with subgroups - looking through all entity prototypes checking "belt_speed" and "max_underground_distance". I might try it out soon.

Your welcome! for myself it "kind of" works modding those filters in.
Tough i still cant use the highest tier belts due the lack of tier 4 and 5 loaders. any chance to remove them from the blueprint script? a optional setting may be nice.

I think it's fixed in 0.2.2.
Existing save files do not update with the change. To force a GUI update, you can disable the mod, save without the GUI, then turn the mod back again.

Edit: The possibly missing loaders and splitters are worked around by falling back to express belts.

Thanks for fixing it! works like a charm now!

about the Loaders: is it possible to add a option for the blueprint to "not" use them? im pretty ok if this will be a "on startup" setting too!

Reason is that my "modpack" dosnt has them at all (they exist but cant be crafted since another mod adds better ones)