How can I manually correct the hyphenation?

I am using LO 4.2.5.2 on Mac OS X, with Libhyphen hyphenator, hunspell etc. installed. I am writing in German, with German spelling/hyphenation activated. No problems, but sometimes, the suggested hyphenation is simply wrong, and I can’t find out how to manually correct/change the hyphenation in LO (this, for once, is easier in MS Word…).
Your help is much appreciated! Thanks.

The Libhyphen files (under <install_location>/share/extensions/dict-de/hyph_* can themselves be edited. There does not appear to be a facility built into LO for editing the entries in these files. This may be due to the multiple / difficult nature of the entries e.g., in the en-GB version there are entries like:

.effic7a7ci4es.
.effi
.effic
.effic2a1c2i2
.efficacie2
.effic7a7cious.
.efficac2io2
.efficacio4u2
.effic7a7cious4ly.
.efficaciou2sl4
.efficacious2ly
.effic7a7cious7ness.
.efficacious1n2
.efficacious1ne4ss
.effic7a7cious7ness's.
.efficaciousnes8s8'8
.efficaciousness's8
.effic7a2cy.
.effic7acy's.
.efficac8y8'8
.efficacy's8