Glossary
Persistent bitmap caching
The Remote Desktop Connection option that writes the bitmap cache to disk, stored in .rdp files as bitmapcachepersistenable:i:1 and on by default.
Persistent bitmap caching is the option in the Remote Desktop Connection client (Experience tab) that keeps the bitmap cache on disk between sessions instead of only in memory. In .rdp files it is stored as bitmapcachepersistenable:i:1. It is on by default in mstsc.
For an investigator, the setting explains whether a cache should exist: with it enabled, the client writes the RDP bitmap cache into the user's profile. Checking Default.rdp for the value is covered in RDP lateral movement: source host artifacts.