The Tool Option bar is very useful (you cannot properly print without it) but the name Option is somewhat misleading : it is not an option to have it, it is a must.
If you take into account that it is empty at the start of LibreCAD when some users will want to customize their interface then they could think it is not important (I did it and search a long time how to print to scale).
I suggest the name be changed to something like Contextual Tool or anything leading to the idea that the content will adapt to the current situation. English native people may find a much better name !
Its importance will be more emphasized in the next documentation...
It could be made unremovable. But I don't believe it happens often someone removes it accidentally.
What happens often is that users don't realize at all it's there and they can / have to make settings there.
Although I agree it is a "must", I also think it is already appropriately named. The word Option in this context applies to each Tool that has a range of Options that can be applied.
It certainly deserves more prominence and should be on by default.
I personally think it would be better if a tool has no options then the bar should be visible saying
"Tool has No Options"
This would imply that other tools do have options that can be seen in the same place when they are active.
Sadly I don't have the programming skills to contribute to the code: my expertise, if I can claim any, is in training and documentation.