Should be possible.
See where the mouse pointer is showing?
Increase the "Range," where it is displaying as a green "1" in a nice black box, change it to 12 (or to whatever is the maximum value between two consecutive notes. It essentially allows you to do wider pitch bend. But beware, too large and it's difficult to do pitch bend. 12 should be ok and is more intuitive).
Sometimes the VST also has a range option inside it. Check and make sure that, if it is there, it corresponds to the value in LMMS VST instrument window. This is rare and I've only noticed it once on a synthesizer VST. A lot of good synthesizer VSTs have portamento option anyways.
Then Ctrl-drag the wheel named "Pitch" into an automation track and automate.
Luckily, musikBear actually has created a video on the exact same topic. The second part of the video shows how to do this.
For your convenience I've timestamped the link so it will start on the second part only. https://youtu.be/Nl4fj0vkQOY?t=637
This should help you understand.