And it looked so pretty!
Okay, I'll try again. This is the basic code without the tie adjustment:
\relative c,, {
\clef bass
\acciaccatura { <ef ef' ~>8 } \tieDown <ef ef'>1 ~ | q1
}
And this is how I tried to address the problem:
\version "2.18.2"
\language "english"
ignoreClash = \override NoteColumn.ignore-collision = ##t
adjustTie = \shape #'((0.0 . 0.0) (0.0 . 0.0) (0.0 . -0.5) (0.0 . -1.0)) Tie
stroke = \override Flag.stroke-style = #"grace"
\relative c,, {
\clef bass
<<
{
\ignoreClash
\tieDown
\stroke \grace { ef8 ~ } ef1 ~ | ef1
}
{
\ignoreClash
\tieDown
\stroke \grace { ef'8 ~ } \adjustTie ef1 ~ | ef1
}
>>
}