I have 3 accounts in Sylvia (KDE).
And there's a good number of applications that came installed, but I don't need them in this particular account.
If I uninstall them while in that account, will they stay in the other accounts?

Thanks

no. if it is removed then none of the other users will be able to execute it.

are you able to remove it from the menu of the user in question ?

I have used Ubuntu for a few years now, but this is my 2nd day using LM.
How can I remove apps from the menu? Is there a Menu Editor?

I should advise you that Mint 18.3 will be the last release that offers and supports KDE Plasma.

Are you saying that it will only be supported until 2021?

Well, if you put it like that.

The thing is, when Mint 19 comes out, in a few months' time once Ubuntu 18.04 (on which it will be based) is released, there will be no KDE version, just Cinnamon, MATE and Xfce. So if you're new to Mint, and will want to upgrade to Mint 19, then I would probably advise you to go for one of those three editions. In saying that, it will probably be possible to backport Kubuntu packages onto Mint, but that won't be officially supported.

I see...
Then, since I just installed LM KDE days ago, I guess I should remove it and install one of the other flavours you mentioned, right?

It is up to you of course, but if you can see yourself using Mint for a while and would like to upgrade it when possible, then yes. You could try adding another of the desktop environments to your current install but I wouldn't recommend it - a fresh install of one of the other editions would be a cleaner way of doing things.

Although I'm a MATE user myself, I would suggest that you try the main Cinnamon edition. It is the most used and thus provides the greatest support. On top of that it is actually developed by the Mint team themselves. However, if you want, you could try live versions of all three and see which you prefer.

If you like KDE, you probably want to use a distro other than Mint since Mint's support for KDE has never been that good and it will be ending as noted above. For a good noob friendly KDE centric distro, I would recommend PCLinuxOS:

http://www.pclinuxos.com/

For a ubuntu based kde distro, you can give Kubuntu a try:

https://kubuntu.org/

However, you might want to wait on Kubuntu until this Spring when the next long term support(LTS) edition comes out.

Other popular KDE centric distros are Mageia, Suse and KDE Neon.

Thanks a bunch for the advice and info on KDE distros.
I don't have a personal preference towards KDE, I only chose the LM KDE due to lack of more info on all this.
As long as the main menu is dynamic enough, with well-organized submenus, like what I have now in LM KDE, then I can easily move to another flavour. I guess I'll go to MATE.

Going back to the original question of this thread...
I hope the LM Mate main menu can be edited.

Right click on the menu->Edit Menu

I use mate on linux mint 18.2 the menu is how you specify and editable