Here are the data structures with brief descriptions:

[detail level 12]

AC_Sim
AM_Modulator
Ampere_ac
Ampere_dc
Ampere_noise
Amplifier
andor4x2
andor4x3
andor4x4
Arc
Area
Arrow
ArrowDialog
Attenuator
Axis
Basic_BJT
Basic_MOSFET
BiasT
binarytogrey4bit
BJT
BJTsub
BondWire
bsim3v34nMOS
bsim3v34pMOS
bsim4v30nMOS
bsim4v30pMOS
Capacitor
Category
CCCS
CCVS
ChangeDialog
Circulator
CoaxialLine
comp_1bit
comp_2bit
comp_4bit
Component
ComponentDialog
Conductor	Label for Node and Wire classes
Coplanar
CoupledTLine
Coupler
CPWgap
CPWopen
CPWshort
CPWstep
Cross3D
CurveDiagram
D_FlipFlop
DataX
DC_Sim
dcBlock
dcFeed
dff_SR
Diac
Diagram
DiagramDialog
Digi_Sim
Digi_Source
DigiSettingsDialog
DigSignal
Diode
DLS_1ton
DLS_nto1
dmux2to4
dmux3to8
dmux4to16
ecvs
EKV26MOS
Element	Superclass of all schematic drawing elements
Ellipse
EllipseArc
EqnDefined
Equation
ETR_Sim
ExportDialog
fa1b
fa2b
FillDialog
GateComponent
gatedDlatch
Graph
GraphicLine
GraphicText
GraphicTextDialog
greytobinary4bit
Ground
Gyrator
ha1b
HB_Sim
HBT_X
hic0_full
hic2_full
hicumL0V1p2
hicumL0V1p2g
hicumL0V1p3
hicumL2V2p1
hicumL2V2p23
hicumL2V2p24
hicumL2V2p31n
hpribin4bit
Hybrid
ID_Dialog
ID_Text
iExp
iFile
ImportDialog
Inductor
iProbe
iPulse
iRect
Isolator
JFET
JK_FlipFlop
jkff_SR
LabelDialog
LibComp
LibraryDialog
Line
LoadDialog
log_amp
logic_0
logic_1
Logical_AND
Logical_Buf
Logical_Inv
Logical_NAND
Logical_NOR
Logical_OR
Logical_XNOR
Logical_XOR
Marker
MarkerDialog
MatchDialog
MESFET
MessageDock
mod_amp
Module
MOSFET
MOSFET_sub
MouseActions
MScorner
MScoupled
MScross
MSgap
MSlange
MSline
MSmbend
MSopen
MSrstub
MSstep
MStee
MSvia
MultiViewComponent
Mutual
Mutual2
mux2to1
mux4to1
mux8to1
mySpinBox
NewProjDialog
nigbt
Node
Noise_ii
Noise_iv
Noise_vv
OctaveWindow
OpAmp
Optimize_Sim
OptimizeDialog
PackageDialog
pad2bit
pad3bit
pad4bit
Painting
Param_Sweep
Phaseshifter
photodiode
phototransistor
PM_Modulator
PolarDiagram
Port
PortSymbol
PostedPaintEvent
potentiometer
Property
PSDiagram
QucsApp
QucsDoc
QucsSettingsDialog
Rect3DDiagram
Rectangle
RectDiagram
RectLine
Relais
Resistor
RFedd
RFedd2P
RLCG
RS_FlipFlop
SaveDialog
Schematic
SearchDialog
SettingsDialog
SimMessage
SmithDiagram
Source_ac
SP_Sim
SParamFile
SpiceDialog
SpiceFile
Subcircuit
SubCirPort
SubFile
SubParameter
Substrate
SweepDialog
Switch
symTrafo
SyntaxHighlighter
HighlightingRule
TabDiagram
tBound
Text
TextDoc	Definition
tff_SR
Thyristor
TimingDiagram
TLine
TLine_4Port
tPoint3D
tPointZ
tQucsSettings
TR_Sim
Transformer
Triac
TruthDiagram
tSpecialChar
TunnelDiode
TwistedPair
vacomponent
VASettingsDialog
VCCS
vcresistor
VCVS
Verilog_File
Verilog_File_Info
VerilogA_File_Info
vExp
vFile
VHDL_File
VHDL_File_Info
ViewPainter
Volt_ac
Volt_dc
Volt_noise
vProbe
vPulse
vRect
VTab
VTabBar
VTabbedDockWidget
VTabInterface
VTabWidget
Wire
WireLabel