We can click the bold button and the text displays bolder. But is there a way to make it even bolder / thicker , after that?
Only the Normal and the Bold properties exist. You can play with the Font Size parameter: a little bit bigger letter seems more bolder.
Yes I was asking no matter which variation we chose. But I guess there is no way to do it in the program
Yes thanks
The “bold” button is a “replacement” command to select a variant of the font. There is no on-off state for font weight. Typographically, it is a continuous parameter. The oldest known example in press industry is the Universe family where weight is selected by a number with a huge range (at least 10-1000 if I remember right). @EarnestAl’s suggestion is the path to follow. You may also find variable fonts configurable with various parameters.
To illustrate @ajlittoz point above, here is a screenshot from Adobe Illustrator. There is only one entry for Montserrat, all the other “fonts” shown in the screenshot from Writer are just different weights of Montserrat
You may add yourself to the CC list for Bug 35538 - Handling of fonts with more than 4 styles (R/B/I/BI) is suboptimal
It is interesting reading.