Some maps have markers for particularly nice viewpoints.
In general*, they consist of "rays" (narrow triangles, circle sections or the like) going from the viewpoint into the directions of the view. Color is not standardized, I've seen them e.g. in blue, red, brown or black - with red often preferred on tourist maps, black on topographic maps.
These are the viewpoint symbol used by openstreetmap: (carto renderer), opentopomap and
There may be variants with the "rays" going only into certain directions which will then indicate the direction of the view.
Example from opentopomap, view towards western directions:
There are further relevant symbols, e.g. opentopomap uses for lookout towers, Kompass .
More "touristy" maps often have more viewpoints marked, whereas the reader of a topographic map may be expected to be sufficiently proficient in map reading to identify obvious view points by themselves. As an example in the Vosges, if the map indicates a ballon with grasland on top, you may be expected to conclude on your own that you'll have a nice view (as outlined in @ChrisH's answer). On a generally wooded hill or from a trail that is winding along in between rocks, it may be impractical to try finding the nice views from topography only (you'd need both large scale map to determine whether there is nothing to block your view immediately, plus large area overview to determine what you'll see further away. Plus you'd need to know whether the indicated type of local vegetation is likely to block your view).
Hoherodskopf (the directed viewpoint example from above). Here, general topography allows to spot this as a good viewpoint: the top of a meadow, just below the forest that covers the highest elevation in the region. The western direction is towards a longish valley that opens into a flat before the next hill range starts some 40 km away.
The viewpoint symbol confirms that - it is actually a regionally famous viewpoint.
A hill sticking moderately out of its surroundings. However, it is completely covered by wood, so less chance of a view. OTOH, it is pretty steep, which increases chances for a view within a wooded area. In fact, there are several view points - but we could not have concluded further than the chance to encounter viewpoints from the topographic map alone here. (There also used to be an observation tower which is not indicated in the map)
The ridge from Kuhkopf to Dachskopf
... currently offers some nice views towards south east. However, there is no whatsover indication in the map. The views exist only because of recent storm and draught damage which has been cleared away. Already in a few years, the viewpoints will be much less because of tall grass, bushes and brambles. That would be too short a timeframe for marking viewpoints on a map.
You may be able identify such areas from satelitte imagery together with the map.
I extended the map section to the north east to include an observation tower which is more permanent.
* I can really speak only for the map symbols as used commonly in Central Europe.
** Kompass is an Austrian map publisher who have lots of touristic hiking maps in their program. Personally, I don't like them much. I've found them not as reliable as I'd have wished (and as I'm used to from the official topo maps or the Alpine club map series).
Personally, I go for the official topographic maps or the Alpine club maps which give me better topographic detail (e.g. finer elevation lines). However, the Kompass maps focus much more on touristic symbols, including viewpoints. In my opinion, it also has low information density, i.e. the amount of information (elevation lines, symbols, ...) are often what I'd find appropriate for a smaller scale map.
So they may meet OP's requirements to help finding viewpoints.