I posted the following in the pre-release forum also:
The files in the “PluginData” folder at the end of the following path:
C:\Users\ (username) \AppData\Roaming\Adobe\UXP\PluginsStorage\PHSPBETA\26\External\ (plugin ID) \PluginData
Did not transfer to the corresponding folder:
C:\Users\ (username) \AppData\Roaming\Adobe\UXP\PluginsStorage\PHSPBETA\27\External\ (plugin ID) \PluginData
When Photoshop Beta v27.0.0 installed.
This means that the user-specific data for that UXP plugin that’s stored in the “PluginData” folder would not transfer over from Photoshop 2025 to Photoshop 2026 if this bug makes it into the general release version of Photoshop 2026. Users would have to manually transfer the files (if they can find them) or, alternatively, would need to recreate all their plugin’s user-specific data that was stored in the “PluginData” folder.
I’m on Windows 11, but have reports from beta testers that the same issue occurred on Mac computers.