Hi,
Select all designators as following:
PCB Filter ==> All Object: IsDesignator ==>Apply.
Select some designator as following:
1/ Edit ==> Select => Toggle Selection ==> mouser right click to designators that you want to select.
2/
Step1: PCB Filter ==> All Object: IsDesignator ==>Apply
Step2: Edit ==> Deselect ==> Outside Area ==> drag on the area you want to select
Good luck.