Firstly, to show an asterisk, or any formatting for that matter, include your code within preformatted text characters `` e.g
'*' + {Root Container.DeviceTagPath} + '/*'
Secondly, how are you opening your device page/popup? Do you pass the path to the device and its name, or do you use a UDTType parameter? If it’s the latter, you’re on your own as I have stayed clear of these for years. If it’s the former, then you should just be able to use the above expression.
There was a bug in v7.9.5, where in the alarm source field you had to include a prefix:
'*:/tag:*' + {Root Container.DeviceTagPath} + '/*'
From memory, will check when at laptop.
Also, I’m assuming that you’re creating a binding expression for the source filter, and not just copying that as text into the source filter text?