There is already a lot of information about how to control your hotkeys in a XenApp session.
At a customer, this still led to some confusion about when and where the config should be done.
This was kind of tricky because they saw that external users experienced different behavior than internal users.
So the first stop was, which interface is used by which user. Internally the users were directed to the internal Citrix Web Interface (yes, old school).
So on the old Web Interface the Default.ica in C:\inetpub\wwwroot\$$websitename$$\conf\ is used to edit the available hotkeys. For a full explanation about this, check https://support.citrix.com/article/CTX140219
The external users are directed to a Netscaler also using the Web interface but this time the one that is available in the Netscaler. So editing the hotkeys must be done in the Netscaler.
I used WinSCP to connect to the Netscaler.
In WinSCP browse to /var/wi/tomcat/webapps/Citrix/Xenapp/WEB-INF/. There you will find the default.ica we need to edit.
Just click the default.ica to open it in an editor and search for the [WFCLIENT] tag.
Default the file looks like this:
Now copy all of the following parameters after the [WFClient] tag:
Ensure to place all the hotkey listings in the file. Map only the required hotkeys and others set to none.
In our case, the customer needs to use Ctrl+F2 and Alt+F2 in an application inside the remote session so Hotkey 5 and 6 need to be set to none like this:
After editing the Default.ica, save it to the Netscaler, and now the Hotkeys of your choice are available in the session.