I often see official hiking tracks going in zig-zag uphill and some of them have short-cuts going straight uphill. These short-cuts are visible, but it is probably expected that most people follow the official street.
Is it a bad practice to add the short-cuts tracks on OSM?
That kind of problem is not limited to these kind of short-cuts, in the Dutch forum there has been a discussion with forest management that wanted to close off some paths and give it back to the nature. I think on the OSM side the agreement was that at least some indication should be present.
If there is any indication that it should not be used, do not map it. Also if there is no indication I would in this case be hesitant to map it. Isnât there some kind of ruling for this area saying you should not walk outside the trails?
You might find the relation:role=alternative helpful.
Hereâs an example â Relation: âŞLionâs Head Summit⏠(âŞ14144595âŹ) | OpenStreetMap)
scroll down to have a look at the alternative path other than the main.
Sounds good.
Do you know if using ârole=alternativeâ will dissuade route planning tools (Komoot, etc.) from taking this track by default?
Ideally the shortcut or alternative path should be shown on the map but only taken by people who explicitly want to take it.
The relation role âalternativeâ is meant for official (and usually marked) alternatives for an official (and usually marked) hiking route. They are not good for unofficial shortcuts or desire/social paths. These should never be added to a hiking route relation.
There is a tag informal=yes (to be added to the highway=path way) for desire paths which is favoured by the US trails access project (see in particular the section âSuggested Taggingâ). But this is all still in a state of discussion.
Personally, I would suggest to not map these shortcuts at all. If they are there as highway=path, they will be used and routed over.
Iâm not very knowledgable with route planning tools.
Komoot does not âtakeâ the alternative route âunless you drop a waypoint.
There are several existing tracks marked as âInformal trackâ, so I have added mine with the same category, which automatically sets the tag informal=yes 
If it is not OK to walk on them (area where hiking outside trail is illegal) then add access=no to them if you or someone else marked them.
Note that deleting existing path is not OK. Adding access info should prevent routing over them.
Though not mapping such features if not mapped already is 100% fine.
The informal=yes tag can be used to note that the shortcut(s) are not official. And as noted by another reply, if they are not allowed (most land managers in my area have rules against short cutting switch backs) then access=no.
I wanted to second the recommendation to check United States/Trail Access Project - OpenStreetMap Wiki
I think your shortcuts would likely be considered âsocial trailsâ and if you map it (Iâm not sure that I would, but Iâm no expert in this matter), looks like youâd want to use the Trail Access Project tagging guidelines. informal=yes and access=no or access=discouraged
Those are official alternative routes. National Parks Cape Town have been actively blocking-up the unofficial short cuts that people created. The unofficial routes destroy the mountain, really not good to encourage their usage. 
Update adding example: Example of genuinely âunofficialâ routes Cape Town National Parks is trying to block off, they are not mapped in OpenStreetMap. The official route is the > shaped route, the faint lines to right are the unofficial routes, they are partially blocked.
Not mapping âillegalâ shortcuts is ok for me. They should especially not appear in route relations.
But I would not delete such paths since that does not prevent from being again mapped by someone not knowing the history.
You canât reliable prevent existing objects to be mapped, it even violates to some extent the OTG rule.
An access tag should suffice.