This.
This is how modern daw should behave. Flawless integration
You think “oh this track needs a little bit of eq” → you smash a key command or a button on your controller and it loads a new instance of Proq3 or whatever your favorite eq is.
Simplify things guys! Cubase and modern daws already have more features and complexity than we could ask for. Now it’s time to simplify the user experience.
(talking about eq here but this apply to ANY plugin really)
Hey you can do that easily with a bit of fiddling with Auto Hot Key if you are on Windows or keyboard maestro if yo sure on Mac.
Depends on your workflow, but you can hoover mouse on insert slot hit command which will trigger AHK/KM sequence for example: Click> send “q 3” -basically will type q 3>[enter]- send enter key"
The logic is to mimic your behavior when you loading plugin so first you “click” on insert slot than you “type” q 3 and it’s showing you “FF pro q 3” and hit “enter” button.
Also there is post (i think from @ggmanestraki or @steve ) on AHK explained how you can load FX on certain insert slot with key command.
I advise you to spent some time getting into AHK or KM(already mentioned numerous times on this forum) and I guarantee it will be the best investment for your workflow. Especially if you are workflow junkie 
In the same spirit we could ask you to use the search function of this forum to see if anybody else has submitted this feature-request already. Additionally have a look at the forum guidelines in order to learn how to vote for a feature-request.
I actually made a really cool version of that using Alfred and Keyboard maestro on Mac.
https://youtu.be/1hb85p7IKRs
I show it around the 12:00 minute mark.
I’m going to make a tutorial on how to set it up if anyone’s interested.
You can do it easily using key commands. When I used Autotune (circa Cubase 6, 7, etc) I had it on a single “K” keystroke, couldn’t be simpler.
Well, on second thought, it was not inserted in the channel, was before DOP was a thing, but was to offline process a stretch of audio, so not really the same thing as the op asks for.
I have it first on my vst list so it only takes 2 clicks to load it, not a big deal…
I have lots of key commands that I shoot from Touch Portal but don´t one for this, anyway, they could add it to the PLE items…
Nice, as a windows user not find it for myself, but would be really cool for others especially the way you presenting it in clear and straight forward manner. Looking forward 
Why not voice Ai if your talking modern ?
Why not speak the command you wish for adding inserts ?
Why not jump ahead of the rest , why stay on Par ?
You could use the talk back in the control room for voice Ai
You could aha
You still need to manually open channel settings right?
Well, not really. You could create an AHK script that sends the keycommand open channel settings for the selected channel, waits a bit, then clicks on the right co-ordinates (but for which slot? You can set-up an imagesearch “IF” condition there, to only do this in a blank slot, but will this work when you change your Cubase colors, hm?), waits a bit, types the plug-ins name, presses enter.
But: You have to be very specific with the co-ordinates. You have to sacrifice actual keys of your keyboard to this command. You need to devise a method to find the next blank insert slot. Imagesearch could help, but see what happens if colors change even by a slight bit)
Then, there are mobile apps like Metagrid for iphoneor Touch Portal for android, where you do this stuff in a more pleasant environment. Create a button, with a label, style and color, that you press and: Sends keystroke for open channel settings, clicks on the right place, (but no way to know what the blank slot is in touch portal), types the plug-in name.
You could break this down to two buttons. Create a plug-in in slot X, then select the plug-in from a set of buttons. It’s somewhat involved, requires maintenance, requires a second device (tablet or phone)
I very rarely use AHK anymore, and Touch Portal I bust out only when I have so big a project that I need quick visibility management. I have set up a nice page for that, with all Channel Filter Types laid out on buttons, and visibility configurations for the project and the mixconsole (16 recallable at once). But I can definitely do without it. It’s just nice to have for very big projects.
As I said it depends on the workflow you looking for.
My suggestion is the simplest and the fastest one where you don’t need to dig much into AHK/KM and it requires insert slots are visible through inspector or mixer channel no matter. In practice simply just position mouse to insert slot hit the key and you get pro-q 3, position bellow hit the command and viola pro-C loaded, ofc you can go deeper as ggmanestraki explained very well!
Also you should mention on which platform you are (Mac/PC) so maybe someone will give you some practical examples, cause you will get few gray hairs till Steinberg implements your request which they have to review the same workflow question i mentioned to be implemented best possible way.