I am trying to make a guide for a video game and there seems to be limit of 10 entry allowed by libre editor. Is there anyway I can change that or should I just create a new index
What is your goal? “Index” entries are intended for chapter, sub-chapter, sub-sub-chapter, … headings. The 10-limit (which is common to all lists) seems reasonable. An outline with more than 10 levels probably reveals a badly structured or overly complicated document organisation.
If your need corresponds to a “map” or relationship between scenes in the game, you should consider some other approach. An advice can be suggested only if you better describe what you want to achieve. Don’t do it according to some solution you already have selected. Revert to the basics, independently from implementation. Use words relevant to the reader, as if you had no electronic documentation.
Don’t forget to mention OS name and LO version. Implicitly, save format will be .odt if you expect full support by LO Writer.