@schulle-123 did you manage to resolve this issue ?. I'm having the same problem.

SAP Business Client 6.5 – PL6 has now been released and the bug has been resolved.

  Thanks Sandra,  SAP have confirmed that CTRL + F doesn't work in PL5 for SAPGUI-tabs, and that it has been resolved in the next version being released in April

I've recently rolled out Business Client 6.5 PL 5 to the end users and they are coming back saying that the CTRL + F (find) function has been disabled.  Has anyone else experienced this ?.