If you want answers within our support KPI timeframes you should raise questions through support portal.
If you want answers from our community, then sometimes you may have to wait for someone to respond.
My understanding is that this is normally managed by Web Servers, whereby as part of the Web Server configuration you can impose a limit on the size of files uploaded. Google your web server name and how to limit file upload size for tips on web server configuration in this area. That won't stop a user selecting a large file but will raise an error when it is uploaded and goes past the limit.
We do have tasks in the system to interrogate the file after selection and before loading ...
https://4js.com/support/issue/?id=FGL-4422https://4js.com/support/issue/?id=GEN-187https://developer.mozilla.org/en-US/docs/Web/API/File... but nothing has come to fruition to date. If you are interested, contact your support contact and get yourself added to the list of requestors for these tasks.
Reuben