With respect to embedding source code - you can wrap it in "pre" and "code" tags, I believe. But are you referring to executing a source block as you might in org-mode? You can also jam whatever custom CSS you want into the https://logseq.com/#/file/logseq%2Fcustom.css file to render code the way you would like.
The Discord channel is also extremely active and the dev team is on there all the time. I am old so I find this all very confusing but they have definitely helped me out several times - https://discord.gg/KpN4eHY
I am a pretty basic user of this, but if there is anything else you want to know, please ask.
