I try to add this line to the Compose file

In fact, I'm unable to load a modified Compose file at all.

I tried creating , modifying (my $LANG is en_US.utf8).

With a modification in place, I've opened a new terminal, tried with su - myloginname, restarting X and completely logging in from the console. The modified Compose never loads, nor does ~/.XCompose block existing lines when I don't add anything or modify an existing line without loading the default one.

I don't know how to proceed. :-(

(Slackware 14.2, openbox)

Works here. Are you sure you're pressing the correct compose key?

On mine, using a uk keyboard and 'gb' keymap, the compose key defaults to shift-altgr, but your Xorg.conf or desktop environment settings (if you're using one) may change it to something else.

alt-gr on it's own is usually configured to <ISO_Level3_shift> rather than <Multi_key>. In operation, it can look like it's doing Compose because some of the mappings will map to 'dead' accent keys, giving a similar effect with certain sequences.

Also, be aware that GTK apps don't tend to use XCompose(XIM), they have their own input methods. I'm not sure what it is currently as I haven't paid much attention to it in a while, but it used to default to SCIM.

Thanks for your response.

I set my compose key in ~/.xinitrc.

It works fine, I can type things like Multi_key ' e to get é and Multi_key e e to get ə, etc.