Custom bin

In my old .net framework 4.8 WF project i have a custom-bin and bin folder. VS is able to resolve custom .dll inside my custom-bin folder but not Rider. Custom-bin is a folder where an associate of my company add custom dll.

What i tried :
 - add ‘probing’ inside WebConfig (<probing privatePath="custom-bin"/>) This is weirdly partialy work for 4 of my 10 dlls
- add dll in assemblies tab

Project run perfecly find without any resolve issues in VS

Any help ?

PS: copy all my custom dll directly in bin folder work fine but this is not a solution