When using "Find availability" fetaure in Schedule board, we can change filters with our own custom fields. The only fields that cannot be changed or used are msdyn_fromdate and msdyn_todate.

If we want to use e.g. custom field bs_mycustomfield instead of msdyn_fromdate for filtering resources, this cannot be done (msdyn_fromdate and msdyn_todate are somehow hardcoded).