If like me you started a game without having "The Mod Configuration Tool" mod enabled, you still have a solution to be able to change the default options of this mod.

you will need to download and activate this mod.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1574469690
and with it executed several commands to save your new values (SAVE your game BEFORE in a new slot).

cm:set_saved_value( [Options], [Value])

three options are modifiable :

mcm_tweaker_obr_en_cost_value ( the cost of respec )
possible values:
disabled (respec have no cost )
firstforfree (first respec have no cost)
enabled (all respec have cost)

mcm_variable_obr_cost_value (value of the cost only need if you have set a cost for respec)
possible values:
100 to 1000

mcm_tweaker_obr_limit_value (limit has only one respect)
possible values:
disabled (no limit)
enabled (only one respect)


example commands :

with this example:
no respect limit
the first respec is free
the following respec costs 500 per level of the character using it

once you had executed your commands and saved your game (in another new slot ^^) , you could quit the game and disable the "Modding DevTool Console" mod.