I have noticed on this beta release that tagging doesn't stick with the project. Furthermore, after working for a while on a project the tagging goes away.
The fix is to exit and restart SE.
SlickEdit Pro 2019 (v24.0.0.3 64-bit)
Serial number: FE11807_BETA
License type: Beta License
License expiration: 2019-10-27 17:00:00
License file: C:\ProgramData\slickedit\24\slickedit.lic
Build Date: August 7, 2019
Emulation: Brief
OS: Windows 7 x64
OS Version: 6.01.7601 Service Pack 1
Memory: 22% Load, 7505MB/32727MB Physical, 7877MB/65452MB Page File, 503MB/8388607MB Virtual
Shell Information: C:\Windows\system32\cmd.exe /q
Screen Size: 1920 x 1080
Project Type: Microsoft Visual Studio Visual C++
Language: .h (C/C++)
Encoding: Automatic
Installation Directory: C:\Program Files\SlickEdit Pro 24.0.0 Beta2\ (non-removable drive,NTFS,21682MB free)
Configuration Directory: C:\Users\rrvt\Documents\My SlickEdit Config\24.0.0\ (non-removable drive,NTFS,21682MB free)
Migrated from: C:\Users\rrvt\Documents\My SlickEdit Config\23.0.1\