Diary for Confluence Cloud is a rebuild for Forge rather than a port of the Data Center code, so a few things work differently. This page collects them all, so nothing comes as a surprise.
Known issues
Keyboard shortcuts are not available
Data Center bound d to open the new-entry editor and ctrl+s to save it. Neither exists on Cloud: a Forge macro cannot register a Confluence-wide keyboard shortcut. Use the editor prompt and the Save button instead.
The editor does not take the cursor on its own
You have to click twice to start writing: once on the editor prompt, and once inside the editor that opens. Atlassian's comment editor component gives the app no way to place the cursor, so it cannot focus itself the way the Data Center editor did.
The entry editor's toolbar is in English
Diary itself is fully translated into English and German. The editor's toolbar, however, belongs to Atlassian's editor component rather than to Diary, and the app has no way to set its language.
Task lists and macros cannot be added from the entry editor
The comment editor's toolbar does not offer them. A task list or macro placed into an entry through the page editor does render correctly in the diary.
Data Center had a comparable limitation — task lists could not be added from its Diary editor either, ever since Confluence 6.14 — with the same workaround.
Differences from Data Center
Sharing a single entry is not available
On Data Center you could click an entry's date to get an anchor link straight to that entry, and opening it scrolled to the entry and highlighted it.
Cloud has no equivalent, and one is not planned. A macro on Cloud is not told the URL of the page it was opened on, so a reader's Diary cannot learn which entry a link meant — and with no page URL to read, it could neither scroll to the entry nor highlight it. Link to the page instead.
The date format is not configurable
Data Center took the date format from Confluence's General Configuration. Cloud writes each entry's date in the reader's own language and conventions instead, so the same diary reads naturally for everyone. The time format is still configurable.
There is no Properties column
Data Center's entry table had a fifth column, Properties, held open for a feature that was never built; it was empty in every row. The Cloud entry table has four columns: Date, Time, From, and Content.
Things that got better
Nothing reloads after you save
On Data Center, saving an entry that contained a macro or a task list reloaded the whole page, because those needed rendering on the server. Cloud renders entries directly, so no save ever reloads the page.
Writes do not block the page
Your change appears on screen immediately and the page is updated in the background, with a Saving… marker on the entry until it lands. If a write is refused, your words are handed back to the editor rather than lost.
Exports carry only the entries
PDF, Word, and page-history views show the entries table alone, without anything else the macro body happens to hold — see Exports, Page History, and Search.