The installation instructions on the site make it very clear that Forge Multipart will be AUTOMATICALLY INSTALLED, however, when I start my MultiMC instance, I get the following message:

Is there a way to MANUALLY install Forge Multipart?

Minecraft version: 1.7.10
Forge Mod Loader version: 10.13.2.1236

If you're interested in the contents of the log file mentioned in the error message, let me know.

i have the same problem on 1.7.10, i have Forge Multipart installed but it keeps saying there is no

same here. Tried a few of the previous versions and it just won't detect multipart.

So how can i solve it if i have same problem?

i have the same problem on 1.7.10, i have Forge Multipart installed but it keeps saying there is no

You can download Forge Multipart here
However, it should be downloaded automatically and I will investigate why it's not later today.

It seems Forge Multipart was removed from the dependencies.info file in the move to MrTJPCore, as seen in this commit: cda69de#diff-6
I will make a quick pull request to fix this.