There are some limitations on this with solely out-of-the-box functionality. I’ve seen some people use the automated groups to pull someone into a group after they complete the last course of Learning Plan 1 (assuming the LP is in sequential order), then use an enrollment rule to auto enroll that person into Learning Plan 2 in the series. This doesn’t show the LPs to the users though so not perfect but might work.
I’ve seen people use a catalog approach like you’re doing - you should be able to force the display order by using the catalog setting of sort by code and making sure the codes on your LPs are in 1, 2, 3 order as you want them to be displayed in the catalog.
The last option, which would require some custom HTML and CSS is to build a custom page with drop-down functionality where users could select various “topic” tiles and then each has a drop-down listing the series of learning plans for them to click and access as they see fit. GuyKat has helped quite a few customers with this custom path so feel free to reach out if you want to explore that and you don’t have the in-house capabilities to achieve it.