Owner or admin creates templates on Settings → Templates. A campaign Message step can use a saved template or a body you type on the step. An InMail template does not make InMail launchable.
Create the template
Sign in as Owner or admin.
Open Settings → Templates.
Enter Name.
Set Channel to LinkedIn, Email, or InMail.
Add a Subject when the channel is Email or InMail. The placeholder says "Required for email / InMail".
Write the Body. You can insert merge variables such as {{first_name}}.
Select Create template. The page flashes "Template created."
LinkedIn is the channel you use for launchable Message steps. Email and InMail templates can exist on this page. InMail sending is not available yet. Review still blocks launch until you remove the InMail step or switch it to Message.
Use a template on a Message step
Open the campaign Sequence. On a Message step, pick the template or keep a custom body. Merge variables on the template work the same as on the step editor.
Do not add an InMail step because you saved an InMail template. InMail cannot launch. Find email cannot launch either. Keep Invitation, Message, and the other launchable steps.