Op is asking how to write a good bass line.
There is no answer for u my friend.
You have to find a process of making basslines that works for you. If you are an individual, a human, you will have a unique expression of music. Find a way to express your music. This is hard. It may take a lifetime. Start immediately, and don't stop.
It may or may not involve a piano roll, a keyboard, a mouse, a bass guitar, a microphone, a turntable, a field recorder, software, hardware...
I feel you though, sometimes the piano roll, and the mother f'ing stupid ass keyboard in general are the least inspirational channels of expression.
Something that I enjoy doing is making a bunch of bass notes with massive, recording each one to a sample, then loading those samples into a sampling drum machine, or a software equivalent, like the FPC (love it) or Poise, or Battery (which I'm selling because I own two copies, $100, it's a good deal - I love that I am putting ads in my posts now, what a dirt bag

) and playing the bass notes on drum pads. This way, you are always in key, you can access a broader range of articulations with ease, and just jam over beats without worrying about you fingering or whatever.
Or, the opposite of that, keeping it in the synth, but assigning macro controls (I use that term because you are working in massive) to a few aspects of the synth that are responsible for shaping the sound, and assigning hardware knobs to the macros, then playing the notes in real time, as you are rocking the knobs.
Keep the notes simple. You don't need a lot of notes to make the bass line move, just a few notes, listen to the beat, and work within it, and work those knobs to get the movement you want.
And THEN, maybe cutting up the recorded bassline, and rearranging it, again by assigning it to pads, or to keyboard, and just reworking it over the beat.
The whole idea is to keep pushing it, it is a process. Grow the bassline, then cut it back, replant it, watch it grow, then cut it back again. In the end, less is more, but getting to that simple perfect groove may have taken countless iterations.
Anyway, best of luck bro.