I normally use the web interface to configure the router, sometimes the command interface.
(as I live in a windows-free environment, winbox is not really for me)

In some screens, for example the Firewall filters or the Routing filters, the list shown on the screen
omits so much information from the actual entry that it is often difficult to obtain a quick overview.
(I know that in winbox it is possible to add extra colums but in the web interface this is not possible)

Therefore I would like to suggest that every page on the web interface get some button or other
widget where you can click and obtain the commandline "print" output for the data shown on
that page, e.g. in a new window/tab or just in the normal output area.

That is probably quite easy to add, at least easier than a configurable column output as found
in winbox. Still it allows a quick overview of what those rules are actually doing. And it would
be useful in many other places as well (interfaces, routes, ipsec, ...)

If the reason for this is the fact you are not running Windows, there are emulators available that could help you to run winbox. Even mikrotik staff uses them in non windows environment.

True, but I also don't like to install software on every computer where I want to access the routers.
Web interface is very good, there is only this minor issue (at least to me).
And it looks like it would be very easy to overcome. After all, there already is the "terminal window".
My enhancement request would be much like a button that opens a terminal window and automatically
issues the command "/topcommand subcommand print" for the particular screen where you are.