@Arsh de Grand, sandbox folder structure is little different than you posted
e.g. "C:\avast! sandbox\S-1-5-21-3817811509-1646742203-1511825224-1001\r4\notepad.exe_{11756c0a-6b6b-11e1-86fa-000c291c592b}\C\Windows\test.txt", where:
- S-1-5-21-3817811509-1646742203-1511825224-1001 is a SID, it's used to distinguish between current and other users (see $Recycle.Bin structure, it uses SIDs as well). If other sandboxes don't use SID (or other marker, they're not multi-user friendly)
- rXX (number) is a reboot counter, it helps sandbox to cleanup previous unused sandbox (webstorage/safezone or any other permanent sandbox doesn't use rXX folder, but own folder's name)
- notepad.exe_{guid} is process identifier; if you execute two notepad.exe processes, each of them must be in own sandbox (i.e. these two processes don't share their sandbox -- this is a difference betweeen e.g. avast sandbox and other sandboxes). You can create one sandbox for those 2 notepad.exe processes if you execute them from the parent's virtualized app (i.e. run cmd.exe in sandbox and then every child process uses the same sandbox, because the 1st notepad's parent is cmd.exe and 2nd notepad's parent is also cmd.exe).
EDITED: there will be "Access Control" sandbox settings in next avast version, it'll be used to mount sandbox structure as a new volume, it'll omit SIDs/rXX folders. Maybe it's what you what, actually.