A 25-perk point version is also available.

In the most up to date versions of Stellaris (2.6.3 and higher) the new launcher may not properly read the mod as updated when you install the updated version over an old version.
In that case, delete the mod from the mods folder, start the launcher, close the launcher, and install the mod again.
The UI elements of the ascension perk slots are partially obscured in the applicable screen; this is left as-is for compatibility with the vanilla UI and low resolution screens, despite looking weird, as it still works fine.

Background

While Stellaris does have full Steam Workshop support and integration, it also has full support for non-workshop mods.
While playing, I became disheartened when I noticed that a lot of the ascension perks were barely more useful than some of the one-shot techs.
(I'm not trying to offend the developers; coming up with ideas is difficult, I know. But, it is also the truth that a lot of the ascension perks aren't exactly "perks" so much as permanent empire-wide modifiers.)
I looked around, and while mods that increase the ascension perk slots exist, they were all on the Steam Workshop.
So, I popped open the Stellaris folder, and made my own.

Description

This mod adds additional ascension perk slots, as well as a repeatable version of the ascension theory technology.
This mod adds 12 additional ascension perk slots, for a total of 20 ascension perk slots. (25 with the optional version.)
The repeatable version of the ascension theory technology that is added is extremely rare, and costs quite a lot of research.
The tech will appear in the society research options, when it does.
The tech will likely only show up late game, and may never show up for those playing in small through medium galaxies until long after the end of a game, unless tech/tradition cost is reduced greatly.

Installation

Place the ascension20.mod file and the ascension20 folder into the following folder depending on your version of the game:

Steam users:
%userprofile%\Documents\Paradox Interactive\Stellaris\mod
Paradox Plaza users:
%userprofile%\Documents\Paradox Interactive\Stellaris Plaza\mod
Microsoft Store and Game Pass users:
%userprofile%\Documents\Paradox Interactive\Stellaris GamePass\mod
(The correct folder may be in a different location with older, unsupported, operating systems, or on versions of the game available from different stores.)

(File and folder are named ascension25.mod and ascension25 for the 25-perk version.)

With the newest version of the Paradox Launcher (v 2020.14 or higher) you may need to start the launcher and go to the mods section, choose Manage All Mods, choose Reload Installed Mods, choose Reload, click done, choose Manage Playset, choose the mod(s) you wish to add to the list, and then choose the button to add them to the playset.

Requesting Assistance

If you do have any issues, please let me know, and I will see if I can help when I am next able to do so.

Releasing Elsewhere

While I would appreciate sending others here to download the mod, I am fine with the modification and subsequent re-release of this mod.