The main it should be multi functional, convenient, easy to use and with minimal settings
*) Pinned, bookmarked words. 1)The windows should be more more narrow 1cm. Words with capital letters, translation with small ones or different colors. Near the word only icon for voice, any other actions in the hidden menu. It's for a good view of words and to save space.
2 ) make it possible to save words in folders and to sort them (data, folder, degree of study),
3 )To copy words and translation after long press or icon, drag&drop to other apps.

*) in the dictionary : easy samples to every meaning of the word,. To pin, bookmark not words, but particular meaning, translation with sample. If sample isn't possible, to make at least translation editable, so you can add sample yourself. To copy words and translation after long press or icon, drag&drop to other apps.

*) Floating Button for floating window or for translation from clipboard board( or share). Make it possible to pin translation, to copy words and translation after long press or icon or as drag&drop, to type or drag&drop words for translation, to add icon for unfolded translation with polysemantic to be able to pin each of them as in the main app (in order to remember the meaning you need instead of learning all the list of meanings), to drag&drop any transaction to any other app.
I like floating button in U-Dictionary.

*) Vocabulary exerciser with minimum requirements :window devided into word and hidden translation, and vice versa ; sort words (data, folder, degree of study), icons with "Remember" "Don't remember", voice, delete, and 3stars that you can mark for yourself :1star for learning in 3days, 2stars for words that you know not well and for revision in 10days, 3stars for reviewing in 1month.

*) Import, export words in txt, xls (word translation)

Thanks in advance for your work.