Can u please add Categories in the left sidebar as like Flarum
You can use the categories widget for this.
The data for the menu isn't present in the categories route, that's why nothing shows... seems odd to put menu in that route, any particular reason? People here can likely find some alternative...
Depending on the theme you are using you can change their locations in the template files. For example for lavender just move this between line 1 and 2. Would have to do it for the other pages as well like categories.tpl etc.
Take a look here https://community.nodebb.org/topic/10794/sticky-sidebar-widgets
Is there a way to get categories by list of category ids with read or write API or I have to make N number of calls to get the categories that I want or there is another way to achieve that?
This is coming in 1.9.0 https://github.com/NodeBB/NodeBB/issues/6433