I think the easiest solution is to do like. It’s longer but involves no coding
1. Create a new Template and paste [!FirstChildRedirect!]. Name the template whatever you want. Assign whatever TVs you need. This will redirect your regular content page to the first "Show" page. Probably "Show 5".
2. Create your normal content page using the template above and paste you content in the content area.
3. Create a new template called Show. Paste the template you would normally paste in the page created above.
3a. You can use wayfinder to show the nav menu (Show 5, Show 20, Show All). So paste your wayfinder call in this template
3b. Put [*showMany*] in the place you want to show the results.
3c. Replace [*content*] with [[GetField? &parent=`1` &field=`content`]] Note: You might need to install GetField snippet. Use GetField to show other TVs
4. Create a new TV called showMany and assign it to this template.
5. Create a page called "Show 5" inside the Content Page and assign the new template.
6. Leave content area empty but paste your Ditto call in the showMany TV. Your Ditto call should look similar to [[Ditto? &limit=`5`]]
7. Repeat 5 to 7 for "Show 10", "Show 50" etc
I’m sorry if I missed any steps