If I install the Logseq OG version, will it automatically replace Logseq 0.10.15 version? If not how should I migrate from logseq 0.10.15 to Logseq OG?
Keepin some 
on this. 
0.10.15 is a dual version, i.e. you can save your data in markdown files or in a database. I have to assume that you chose database because, otherwise, with markdown files there is nothing to migrate other than saving the various customizations.
I was using an MD graph for a long time before the DB version came out. I’m pretty sure I just installed Logseq OG and pointed it at my graph.
I think i then actually installed the first DB version (2.0.1 I believe) and it just overwrote 10.x (whatver 10 version I was on) and now I have them running side by side. Although I haven’t explored the DB version as much as I want yet because I haven’t sorted out sync.
does that answer your questio?
Thanks for your reaction. I will first test Logseq OG in combination with my MD graph in a secure environment. The DB version is too early for me. Some of my plug-ins for instance printing to pdf are not working yet.
Yeah I’m going to be doing the same. Also for me I have to rebuild all my queries which are a major part of my workflow. Not impossible but it takes time..
In case it’s relevant to you there is a pull request for a system that will sync locally between say your phone and your computer. I only mentioned because I’ve been using syncthing and that’s not currently an option in the same way.