IBus 1.5.19 is now released and it’s available in Fedora 29.
# dnf update ibus
Also it’s available in Fedora Copr for Fedora 28.
This release moved the input focus on IBus emojier to pre-edit areas on each application upon the several feedbacks of the previous implementation. Therefore now your input focus is not changed during typing emoji annotations, Unicode name or Unicode code points with Ctrl-Shift-e. 
Ctrl-[f|b|n|p], Ctrl-Shift-[n|p], PageUp, PageDown, Escape shortcut keys have been available since previous IBus versions and you can check ibus-emoji(5) man page.
The pre-edit area supports multi-byte annotations with your current input method engine (IME). To configure the language of emoji annotations, you can run
ibus-setup and go to “Emoji” tab. English annotation is always available whether you choose anther language or not. 
E.g. In ibus-anthy, Set English mode and type Ctrl-Shift-e, Ctrl-j (to enable Hiragana mode), e, g, a, o, Ctrl-j (to revert to English mode), Space
In case you’d like to show emoji category, you can type Ctrl-Shift-e and just Space without any annotations or run
ibus emoji command. Unicode category is also available from the bottom of the emoji category.
A new annotation “history” is implemented to show the emoji characters which were output previously.
Also the feature of typing Unicode code points with Ctrl-Shift-u is separated from the consolidated features of Ctrl-Shift-e, for who does not wish to show the lookup window of emoji candidates but just output the specified Unicode character with the code point. Ctrl-Shift-e still can cover the Unicode code point. E.g. if you type, Ctrl-Shift-e, 100, Space, Space, both the Unicode character (Ā) of code point U+100 and emoji character (💯) of “100” annotation can be popuped. The both shortcut keys can be customized with
IBus emojier’s lookup window is now changed from the focused window to the popup window not to take the input focus. But popup windows under Wayland always take the focus and cannot locate the window position if the popup window does not have a parent window, the UI is different between Xorg desktops and Wayland desktops.
- Use desktop’s lookup window which shows emoji candidates of one dimension and does not list up the available annotations and code points
- No menu item on panel icon to show emoji category so you could run
ibus emojicommand or implement a special indicator in the panel
- Use IBus emojier lookup window which shows emoji candidates of two dimensions and list up the available annotations and code points
- Menu item “Emoji choice” is available on right click menu on IBus panel icon to show emoji category
Also pre-edit of compose key typing is now available. IBus uses
setxkbmap command to set keymaps internally in non-GNOME desktop so you can show the current compose keys with
setxkbmap -query command. E.g. Configure of Right window key with
setxkbmap -option compose:rwin. I think your desktops can save the compose key setting. If your desktop does not support it, probably you might like to save the setting in
GNOME-Shell sets keymaps and compose keys in GNOME desktop and you can configure compose keys with
ibus-extension-gtk3by manual to enable it, whose install path depends on distributions. Fedora path is
ibus-setup, The Unicode data is cleaned up unexpectedly until you restart ibus. This is fixed in ibus master after IBus 1.5.19.