It probably is as easy as taking off/commenting out the sendCoinsPage->clear(); function on the line 528 in bitcoingui.cpp.
I'll check it out.
If we are going to remove it, we should also have a "Clear all Entries" button on the Send Coins page, so you don't have to clear every transaction invidually.
EDIT:
Well this is funny. Bitcoin-qt refuses to compile (at least using MingGW) after bringing my fork up-to-date.
EDIT 2 :
Commit
https://github.com/laanwj/bitcoin-qt/commit/010c4fc0b5ca8ceccf15417b833bea4ce1016f43 won't compile on Windows while
https://github.com/laanwj/bitcoin-qt/commit/5dd7318db75db580d602c72a2322df97d8712233 compiles just fine.
EDIT 3 :
Okay, it seems the commit
https://github.com/Matoking/bitcoin-qt/commit/99cec89cb369beb8dce6c92db837bb5951f627d5 breaks compiling on Windows. Everything before it compiles just fine.
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0xee0): undefined reference to `CreateDCA@16'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0xeef): undefined reference to `CreateCompatibleDC@4'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0xf08): undefined reference to `GetDeviceCaps@8'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0xf23): undefined reference to `GetDeviceCaps@8'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0xf44): undefined reference to `CreateCompatibleBitmap@12'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0xf5b): undefined reference to `SelectObject@8'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0xf7e): undefined reference to `GetObjectA@12'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0x1024): undefined reference to `BitBlt@36'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0x103b): undefined reference to `GetBitmapBits@12'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0x10b0): undefined reference to `SelectObject@8'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0x10bb): undefined reference to `DeleteObject@4'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0x10c8): undefined reference to `DeleteDC@4'
d:/qtsdk/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../libcrypto.a(rand_win.o):rand_win.c:(.text+0x10d5): undefined reference to `DeleteDC@4'
EDIT 4 :
I've worked around it temporarily by using the old .pro file. Also, implemented what kripz suggested alongside with a Clear all button :
https://github.com/Matoking/bitcoin-qt/commit/609acbf43d8d66102878e47a826c037edc270e46