How to unambiguously indicate inflections where letters are sometimes removed?

Dictionaries probably spell out the cases that cannot fit the "-" type.

jump -s -ing -ed -ed
[Or, in regular cases like this, may leave them out completely]
run -s -ning ran run
drink -s -ing drank drunk
be am is are -ing was were been

Actually, modern on-line dictionaries, not pressed for space, may spell them all out.
jump jumps jumping jumped jumped

It is not a necessary function of dictionaries to provide an exhaustive list of the inflections of verbs or nouns. The bigger and more comprehensive the dictionary, the more likely it is that this kind of detail might be included. The definition of dictionary in the Cambridge English Dictionary on line makes this clear.

a book that contains a list of words in alphabetical order and explains their meanings, or gives a word for them in another language; an electronic product giving similar information on a computer, smartphone, etc.:

There is no commitment here to go into their morphology.

There are however other ways in which some dictionaries, including the Cambridge English Dictionary, can and do provide the information you seek. Most larger dictionaries provide examples of the standard uses of a word. Among the examples for dance provided by CEG, for example, is "dancing". [https://dictionary.cambridge.org/dictionary/english/dance]

Similarly for the verb 'slip' it provides examples of the past tense, where the final 'p' is doubled. The participle use is not exemplified, but an attentive searcher ought to be able to realise if the past has a doubled 'p', so must the present participle.